Control of electric motors.



No. 677,038. I O Patented June 25, [90L F. A. MEBBICK. CONTROL OFELECTRIC MOTORS. (Application modliov. 14, 1900. (No ModeL) I v 2shun-gum n.

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No. 677,038. Patentad 1m 25, l90l. F; A. MERRIQK. CONTROL OF ELECTRICMOTORS.

(Application Med Nov. 14, 1900.)

2 Sheets-Sheet 2.

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' WLMQ A W ATTORNEY.

UNITED STATES PATENT OFFICE.

FRANK A. MERRICK, OF JOHNSTOWN, PENNSYLVANIA, ASSIGNOR TO THE LORAI-NSTEEL COMPANY, OF PENNSYLVANIA.

CONTROL OF ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent N 0. 677,038, dated June25, 190] Application filed November 14, 1900. fierial No- 36,476 (Nomodel-J electric motors, and is designed to provide a system ofseries-parallel control in which the change from series to parallel ismade without the use of external resistance and by a series of stepswhich provide a nearly uniform acceleration in the speed of the motors,such steps being effected without at any time opening entirely themotor-circuit.

My improved system is in some respects similar to that described andclaimed in my Patent No. 645,116, dated Marchl3, 1900, but

differs therefrom in several important motor combinations, as willhereinafter appear.

It consists generally in a system of seriesparallel control in which thechange from series to parallel is efiected by first connecting th fieldsof the motors in parallel and in series with the armatures, which are inseries with each other, shunting one of the motors with the field of theother motor ,'then temporarily cutting the shunted motor out ofcircuit'and immediately thereafter reconnecting it in circuit in suchamanner that it is shunt-ed by the armature of the. other motor, and thenagain removing the shunted motor from the circuit and again connectingit'in circuit in parallel with the first motor.

My invention also'consists in the novel step or motor combination inwhich a motor is shunted by thefield of another motorwhose armature isalso in circuit and is carrying the current of both the shunting-fieldand the shunted motor.

It also consists in the novel combination of steps or motor combinationsand subcombinations thereof, all as hereinafter described and pointedout in the appended claims.

In the accompanying drawings, Figure 1 is a diagram showing adevelopment of a controller and circuit connections such as may beemployed in the practice of my invention, I

and Fig. 2 is a view showing graphically the motor combinations whichare effected by the controller in its different positions and whichconstitute my improved method of motor control.

In the drawings two motors are shown, their armature and field coilsbeing respectively designated as Ar Ar and Fe F62. The motor whoseelements are designated Ar and Fe will hereinafter be referred to asmotor No. l and the other motor as motor No. 2.

Referring now more particularly to Fig. 2, the first three positionsrepresent the usual v resistance-steps, which I prefer to employ instarting the motors, the external resistance used in these steps beingdesignated R. Po-

sition 4 shows the motors in straight series,

the resistance having been entirely removed,

and is not again used until the controller reaches position 3 on itsreturn movement. The next running position is that indicated at 5, inwhich the fields are connected in parallel and in series with theconnected armatures; The efiect of this position is of course to reduceby approximately onehalf the total ohmic resistance of the fields, andthereby proportionately reduces their strength relatively to thearmatures, each of which carries the current of both fields, andacorresponding increase in speed results. To pass from position 4'toposition 5, it'is necessary, of course, to remove one of the fieldstemporarily from circuit in order that it may position gives aconsiderable increase in speed over position 5, sincethe armatures arenowin parallel, but undue acceleration is prevented by reason of thefact that the field of motor No. 1 is in series not only with its ownarmature, but also with motor No. 2. This arrangement also preventsarmature No. 1 from taking an undue proportion of current, since it hasa high counter electromotive force, due to the strength of its field. Topass from position 5 to position 6 without entirely opening themotorcircuit and without introducing wasteful external resistance and atthe same time to avoid objectionable circuit conditions is one of themain problems solved by my invention. The chief difficulty presented bythis transition ,i Fig. 1. velopment of a rotary drum upon which are.

consists in the fact that it is necessary to change the armatures fromseries to parallel relation at a time when they are carryingconsiderable current and have attained a considerable speed. To do this,it isof course necessary to open the circuit through one of the ar-.matures. The most obvious way of doing this is to short-circuit and thenremove the armature from circuit after having first killed or removedits field. This, however, is not feasible in practice, for "the reasonthat the ordinary throw of the controller-handle is made with suchrapidity that the opened field does not have time to lose its residualmagnetism before the armature is short-'circuited, .and the motormomentarily acts as a generator in 5 a closed local circuit, causing itto buck or flash severely at the brushes. Other circuit changes tried by'me have also proven objecti'onable, either as causingdifficulty in themotors or undue arcing in the controller. I; have therefore devised thesteps herein shown, wherein the circuit of one of the fields (see;position 5) is temporarily opened, and thei field is then reconnected'in shunt to the other i motor. (See position 5 Immediately fol-i lowingthis the circuit through the shunted? motor'is opened, (see position53,) and the con 5 nection's of position 6 are established. Byi puttingthe field of one motor in shuntto the; other motor as a whole, with thearmature of} the shunting-field in series therewith, comparativelylittle current will pass through the i shunted motor, which can then bereadily disi connected, the change in connections being, effectedwithout trouble in the motors or at% the controller. The transition fromthe comj bination of position 6 to the full multiple po-} sition shownat position 7 is readily effectedi by. again opening the circuit ofmotor No. 2, as indicated at position 6, and then connecti ing it in,parallel with the other motor.

Any suitable type of controller may be em, ployed for carrying 'out myimproved system of control. prefer, however, to employ a controller ofthe usual type, such as shown In this figure 0 represents a demounted aplurality of contacts (designated by the reference characters 0 0 c&c.,.to and including 0 which are engaged in different positions of thedrum by the stationary con-' tact-fingers, (marked F F F -&c., to F Thebroken vertical lines on the drum develop'mentflindicat'e the severalpositions of the drum corresponding to the motor combinations shown inFig. 2.

RS designates a combined reverse andcut out switch of well-known typehaving 'a'pl'u rality of movable contacts 2 and fixed conta'ct-fingersSto S inclusive. This "switch is shown only for the purpose ofillustrating the,;:motor-circuits complete, and in tracing the circuitsit will besufficient toconsiderthe fingers -S to S as resting on thecontacts 2 to; '2 on the vertical line -marked ahead. The;

' Fe at both terminals thereof,

arrangement and electrical connections of the 8", contacts z" 2 fingerSF, field F finger S contacts 2 2 fingers S F contacts 0 c fingers F S,contacts z e finger S field Fe, finger S contacts e2 fingers S Fcontacts 0 c to finger F and through the resistance R to ground.

Positions 2 and 3 simply short-circuit successive sections of theresistance Rbythe engagement, respectively, of the grounded contacts c cby the fingers F and F, and at position 4 the entire resistance isshort-circuited by the finger F engaging the contact 0 At position 4:thecontact-finger F lapsover onto the "contact e and momentarilyshortcircuits the field Fe which is immediately thereafteropen-ci-rcuited by the finger F leaving the contact 0 at :position 4 Theother circuit connections remain as before.

At position 5 the series connections of the .arrhatures remain asbefore. The engagement of finger F with the contact 0 reconnects thefield Fe in series with the armatures, while the-conti-nuedengagement ofthe finger F with contact 0 connects field Fe in parallel with fieldF62.

At position 5 the only change effected is that fingers F and F have leftthe respective contacts 0 0 which opens-thecircui'tof field giving twobreaks in series.

contacts 0 and e and the fingers F and F touch the respective contacts 0and c. The current after passing through armature Ar" will thereforedividebetween the contacts 0 and 0 one part going by finger F to fingerF contacts 0 e fingers F S contacts 2" a finger S, field Fe finger Scontacts 2 5 2 fingers S F to grounded contact 0 The *otherpath is bycontact 0 to contact 0 to fingers F S, to contacts z 22, finger S fieldFe, finger S contacts 2' 2 finger S finger S to grounded contact 0At'position 5 the fingers F F ,-F F and F 'hav'e left the respectivecontacts 0 0 c 0 0 and fingers F F and F F and F are engaging,respectively, contacts 0 e e e 0 This, it will be seen, leaves motor No.1 in circuit and breaks the circuit of motor No 2 at'threediffe'rentpoints-via, between contacts 6 0 between contacts o and a",and between contacts 0 and 0 At position 6 all the contact engagements aa 110. At position5 the finger F is lapping both .8", contact 58,finger. S armature'Ai finger tering the character of the invention.

of position 5 are preserved, and in addition contacts 0 e 0 0 and e arealso engaged by the respective fingers F, F?*, F F and F The current nowdividesbetween the contacts 0 and 0 one part going by fingers F Scontact Z and finger S to armature Ar, thence to finger F contact 0contact o finger E finger S, contacts 2 .2 through field Fe to contacts2' a fingers S F to grounded contact 0 The other path is from contacts 0e to fingers F 8 contact a finger S armature Ar finger F contacts c 0fingers F 5 contacts .2 2 to and through field F62 to contacts 2 2fingers S F to contacts 0 o when it unites withthe first path.

At position b" the connections are precisely the same as at position 5the circuit through motor No. 2 being opened at a number of points inseries.

' At position 7 the circuit is as follows: from T to'contacts 0 0 thecurrent dividing as before, one part going by F S 2 A1", F o o F S, z,22, Fe, S 2, 2 S F to grounded contact oiand the other part by e 0fingervF", S 2 S Ar F e 0 F, 8", Z .2 8, F62, S 2 .2, S F to groundedcontact 0 7 It will be obviousthat the, particular contact arrangementabove described is merely illustrative and that various otherarrangements may be employed. Neither do Iwish to limit myself tounimportant details herein described for the purpose of presenting acomplete working embodiment of my invention, since these may be changedwithout al. I do not,- however, claim herein,exc'ept in combinationwiththe other steps,- the' motor combination or step shown at position6, as I be 'lieve such combinationor step to be the inveniion of FrankWV. Garrett, of J ohnstown,

1 Pennsylvania, as described and claimed in his pending application forpatent, Serial No. 28,324. p 7

Having thus described my invention, what I claim, and desire to secureby Letters Patent, is, Y I

1. The method of controlling a pair of electric motors, which'consistsinstarting them from a position of rest connected in series witheachother, then connecting their fieldcoils in parallel and in serieswith the seriesconnected armatures, then shunting'one motor with thefield of the. other motor, then shunting one of the motors with thearmature of the other motor, and finally connectingboth motors inparallel. 2. The method of shifting a pair of electric motors fromseries to parallel relation, which consists in first changing the fieldsonly from series to parallel, then shunting one motor 3. The method ofshifting a pair of electric motors from series to parallel relation,which consists in first changing the fields only from series toparallel, then opening the circuit of one of said fields andreconnecting it in circuit in shunt to the other motor, then opening thecircuit of the shunted motor and shift ing the connections to place saidmotor in parallel with the armature only of the other motor, and inseries with the field thereof, and finally connecting both motors as awhole in parallel.

4. The method of shifting a pair of motors from series toparallelrelatiomwhich consists in first changing the fields only fromseries to parallel, then shunting one motor with the field of the othermotor, then shunting it with the armature of the other motor, andfinally connecting both motors in parallel.

5. The method of shifting a pair of motors from series to parallelrelation, which consists in first changing the fields only from seriesto parallel, then without entirely opening the motor-circuit, changingthe connections of the motors to place them in a relation in which onemotor is shunted by the armature of the other, motor, -and.thenconnecting both motors as a whole in parallel.

.6. The herein-described method of changinga pair of motors from seriesto parallel relation, which consists in first changing the fields onlyfrom series to parallel, then shunting one motor with the field of theother motor, with the armature of the shunting-field still in series,then shunting'the same motor with the armature of the other motor, withthe field of the shunting motor in series, and

. finally connecting both motors in parallel.

. 7. In the control, of electric motors, the

step which consists in shunting one motor with the field of the othermotor.

8. In the control of two electric motors, the step which-consists inconnecting the armatures of both motors and the field of one motor allin series, with the same field and its correspondin g armatureshunted bythe other field.

motor, then connecting said coils as a shunt,

to the other motor, andthenopeningthe circuit of the shunted motor andrearranging its connections to give the desired relation'of the twomotors.

too

Intestimony whereof I have aifixed my signature in presence of twowitnesses.

FRANK A.-MERRICK.

Witnesses:

CORA G. 00X, 'H. W. SMITH.

